Non-viral vectors for gene delivery have attracted much attention in the past several decades due to their potential for limited immunogenicity, ability to accommodate and deliver large size genetic materials, and potential for modification of their surface structures. Major categories of non-viral vectors include cationic lipids and cationic polymers. Cationic lipid-derived vectors, which were pioneered by Feigner and colleagues, represent some of the most extensively investigated systems for non-viral gene delivery (Feigner, et al. Lipofection: a highly efficient, lipid-mediated DNA-transfection procedure. PNAS, 84, 7413-7417 (1987)) (Templeton, et al. Improved DNA:liposome complexes for increased systemic delivery and gene expression. Nat. Biotechnol. 15, 647-652 (1997)) (Chen, et al. Targeted nanoparticles deliver siRNA to melanoma. J. Invest. Dermatol. 130, 2790-2798 (2010)).
Cationic polymer non-viral vectors have gained increasing attention because of flexibility in their synthesis and structural modifications for specific biomedical applications. Both cationic lipid and cationic polymer systems deliver genes by forming condensed complexes with negatively charged DNA through electrostatic interactions: complex formation protects DNA from degradation and facilitates its cellular uptake and intracellular traffic into the nucleus.
Polyplexes formed between cationic polymers and DNA are generally more stable than lipoplexes formed between cationic lipids and DNA, but both are often unstable in physiological fluids, which contain serum components and salts, and tend to cause the complexes to break apart or aggregate (Al-Dosari, et al. AAPS J. 11, 671-681 (2009)) (Tros de Ilarduya, et al. Eur. J. Pharm. Sci. 40, 159-170 (2010)). Additionally, although some work indicates that anionic polymers or even naked DNA can provide some level of transfection under certain conditions, transfection by both lipids and polymers usually requires materials with excess charge, resulting in polyplexes or lipoplexes with net positive charges on the surface (Nicol, et al. Gene. Ther. 9, 1351-1358 (2002)) (Schlegel, et al. J. Contr. Rel. 152, 393-401 (2011)) (Liu, et al, AAPS J. 9, E92-E104 (2007)) (Liu, et al. Gene Ther. 6, 1258-1266 (1999)). When injected into the circulatory system in vivo, the positive surface charge initiates rapid formation of complex aggregates with negatively charged serum molecules or membranes of cellular components, which are then cleared by the reticuloendothelial system (RES).
More importantly, many cationic vectors developed so far exhibit substantial toxicity, which has limited their clinical applicability (Tros de Ilarduya, et al. Eur. J. Pharm. Sci. 40, 159-170 (2010)) (Gao, et al. Biomaterials 32, 8613-8625 (2011)) (Feigner, et al. J. Biol. Chem. 269, 2550-2561 (1994)) (Kafil, et al. BioImpacts 1, 23-30 (2011)) (Lv, et al. J Contr. Rel. 114, 100-109 (2006)). This too appears to depend on charge: excess positive charges on the surface of the complexes can interact with cellular components, such as cell membranes, and inhibit normal cellular processes, such as clathrin-mediated endocytosis, activity of ion channels, membrane receptors, and enzymes or cell survival signaling (Gao, et al. Biomaterials 32, 8613-8625 (2011)) (Feigner, et al. J. Biol. Chem. 269, 2550-2561 (1994)) (Kafil, et al. BioImpacts 1, 23-30 (2011)).
As a result, cationic lipids often cause acute inflammatory responses in animals and humans, whereas cationic polymers, such as PEI, destabilize the plasma-membrane of red blood cells and induce cell necrosis, apoptosis and autophagy (Tros de Ilarduya, et al. Gene delivery by lipoplexes and polyplexes. Eur. J. Pharm. Sci. 40, 159-170 (2010)) (Gao, et al. Biomaterials 32, 8613-8625 (2011)) (Lv, et al. J. Contr. Rel. 114, 100-109 (2006)). Because of these undesirable effects, there is a need for highly efficient non-viral vectors that have lower charge densities.
Synthesis of a family of biodegradable poly(amine-co-esters) formed via enzymatic copolymerization of diesters with amino-substituted diols is discussed in Liu, et al. J. Biomed. Mater. Res. A 96A, 456-465 (2011) and Jiang, Z. Biomacromolecules 11, 1089-1093 (2010).
Diesters with various chain length (e.g., from succinate to dodecanedioate) were copolymerized with diethanolamines with either an alkyl (methyl, ethyl, n-butyl, t-butyl) or an aryl (phenyl) substituent on the nitrogen. The high tolerance of the lipase catalyst allowed the copolymerization reactions to complete in one step without protection and deprotection of the amino functional groups. Upon protonation at slightly acidic conditions, these poly(amine-co-esters) readily condense DNA and form nano-sized polyplexes. Screening studies revealed that one of these materials, poly(N-methyldiethyleneamine sebacate) (PMSC), transfected a variety of cells including HEK293, U87-MG, and 9L, with efficiency comparable to that of leading commercial products, such as Lipofectamine 2000 and PEI14. PMSC had been previously used for gene delivery, but the delivery efficiency of the enzymatically synthesized materials was approximately five orders of magnitude higher than any previously reported (Wang, et al. Biomacromolecules 8, 1028-1037 (2007)) (Wang, et al. Biomaterials 28, 5358-5368 (2007)). However, these poly(amine-co-esters) were not effective for systemic delivery of nucleic acids in vivo. This may be due to the fact that the polyplexes formed by these polymers and genetic materials (1) do not have sufficient efficiency for in vivo applications and/or (2) are not stable enough in the blood and fall apart or aggregate during circulation.
Accordingly, there remains a need for non-viral vectors suitable for efficient systemic in vivo delivery of nucleic acids with low toxicity.
There is also a need for formulations of polymeric nanocarriers which can be prepared in as few steps as possible and in which the molecular weight and/or polymer composition can be easily controlled.
Therefore, it is an object of the invention to provide formulations that have improved polymers that can effectively deliver therapeutic, diagnostic, and/or prophylactic agents in vivo, and methods of making and using thereof.
It is an object of the invention to provide formulations that have improved polymers that can effectively deliver therapeutic, diagnostic, and/or prophylactic agents to tissues with low pH tissue environments or cellular compartments in high efficiency in vitro and are suitable for in vivo delivery of agents.
It is an object of the invention to provide methods of making formulations that have improved polymers for systemic delivery of therapeutic, diagnostic, and/or prophylactic agents to low pH tissue environments or cellular compartments in high efficiency in vitro and are suitable for in vivo delivery of agents.
It is also an object of the invention to provide methods of using formulations that improved polymers for systemic delivery of therapeutic, diagnostic, and/or prophylactic agents to low pH tissue environments or cellular compartments in high efficiency in vitro and are suitable for in vivo delivery of agents.